diff --git a/internal/apijson/field.go b/internal/apijson/field.go
index 854d6dd7..53349a7c 100644
--- a/internal/apijson/field.go
+++ b/internal/apijson/field.go
@@ -14,7 +14,7 @@ type Field struct {
 	status status
 }
 
-// Returns true if the field is explicitly `null` _or_ if it is not present at all (ie, missing).
+// IsNull returns true if the field is explicitly `null` _or_ if it is not present at all (ie, missing).
 // To check if the field's key is present in the JSON with an explicit null value,
 // you must check `f.IsNull() && !f.IsMissing()`.
 func (j Field) IsNull() bool    { return j.status <= null }
diff --git a/internal/apijson/subfield.go b/internal/apijson/subfield.go
index 6f9e2bdb..2ee3845d 100644
--- a/internal/apijson/subfield.go
+++ b/internal/apijson/subfield.go
@@ -1,8 +1,9 @@
 package apijson
 
 import (
-	"github.com/openai/openai-go/packages/resp"
 	"reflect"
+
+	"github.com/openai/openai-go/packages/resp"
 )
 
 func getSubField(root reflect.Value, index []int, name string) reflect.Value {
@@ -55,10 +56,10 @@ func setMetadataExtraFields(root reflect.Value, index []int, name string, metaEx
 }
 
 func (f Field) toRespField() resp.Field {
-	if f.IsNull() {
-		return resp.NewNullField()
-	} else if f.IsMissing() {
+	if f.IsMissing() {
 		return resp.Field{}
+	} else if f.IsNull() {
+		return resp.NewNullField()
 	} else if f.IsInvalid() {
 		return resp.NewInvalidField(f.raw)
 	} else {